The preamplifier that put Audio Research on the map - a valve phono/line stage of 1972 that stayed in production until 1976 and was upgraded by the factory through SP-3A and SP-3A-1 revisions.
The ARCDB model page's own historical letter says "Back in 1971, Audio Research introduced the SP-3", while the database fields read 1972–1976. Both readings are kept; the confidence stays medium.
Valve equipment: 400-500 V is present on the plates and stored in the supply after switch-off. ARC units are valve-matched at the factory - replacement sets must be bought as matched quads/pairs.
Marks that can be entered for this maker: Model / catalogue number, Model / catalogue number, British capacitor code (Hunts, Mullard), Japanese capacitor code (Nichicon, Chemi-Con, ELNA), EIA component code.
Nothing predates 1972; components only push the date later.
Sold-listing reading: fair EUR 3,500, good EUR 3,500, excellent EUR 3,500 EUR · 2 sold listings (thin sample — indicative only) · as of 2026-10-17. Asking prices only - these are live listings, not completed sales. 2 listing(s) in EUR observed on 2026-10-17 via the HiFi Shark marketplace aggregator; with fewer than three observations the same min/median/max is recorded as an estimate, not as an asking aggregate, which is a reading of the ask spread, not a condition grading. Listings in other currencies were seen and counted for the spread but are not converted here (see the journal): NOK x1, TWD x1, USD x1.
Evidence: ARCDB — Audio Research model database · HiFi Shark — live listings aggregator